What is a normal prostate volume in adult males?

Normal Prostate Volume in Adult Males

The normal prostate volume in adult males ranges from approximately 20 to 30 mL, with an average of about 24 mL in men aged 50-60 years, increasing to approximately 38 mL in men aged 70-80 years. 1

Age-Related Changes in Prostate Volume

• Prostate volume increases continuously with age, with an average growth rate of approximately 2% per year for total prostatic volume 2
• In men aged 50-80 years, mean prostate volume increases from 24 mL in the youngest age group (50-60 years) to 38 mL in the oldest age group (70-80 years) 1
• The central hypoechoic area of the prostate grows at a faster rate (3.5% per year) than the total prostatic volume 2
• The average doubling time for total prostatic volume is approximately 35 years 2

Normal Range and Distribution

• Studies show that 95% of men aged 55-74 years have a total prostate volume greater than 20 mL 2
• Prostate volumes in the range of 30-40 mL are considered borderline enlarged, while volumes above 40 mL are generally considered enlarged 3
• In clinical trials for BPH treatment, the mean baseline prostate volumes reported in various populations were:
  • American men with LUTS secondary to BPH: 36.3 mL (SD 20.1) 3
  • European men with LUTS: 36 g 3
  • American men with symptomatic BPH: 37.6 g 3
  • Multinational men with LUTS: 54.5 cm³ 3

Clinical Assessment of Prostate Volume

• Digital rectal examination (DRE) tends to underestimate prostate volume compared to transrectal ultrasound (TRUS) measurement 4
• The underestimation increases with increasing prostate size:
  • 9-12% underestimation for volumes 30-39 mL
  • 17-27% underestimation for volumes 40-49 mL 4
• DRE can categorize prostates with reasonable accuracy:
  • Flat or normal prostates on DRE typically have volumes <30 mL (positive predictive value 94.1%)
  • Moderately or markedly enlarged prostates on DRE typically have volumes ≥30 mL (positive predictive value 80.8%) 5
• TRUS is more accurate than DRE for precise volume measurement, particularly for prostates that feel slightly enlarged on DRE 5

Clinical Significance of Prostate Volume

• Prostate volume correlates with serum PSA levels - as prostate volume increases, PSA values tend to increase 6
• Prostate volume is an important consideration in treatment selection for BPH:
  • 5-alpha reductase inhibitors (5-ARIs) like finasteride are more effective in men with larger prostates (>30 mL) 7
  • In the Medical Therapy of Prostatic Symptoms (MTOPS) trial, the mean prostate volume was 36.3 mL, with 16% of patients having volumes ≤20 mL, 18% having volumes ≥50 mL, and 66% having volumes between 21-49 mL 7
• Surgical treatment recommendations for BPH often consider prostate size:
  • Transurethral incision of the prostate is recommended for prostate size <30 mL 3
  • TURP is recommended for prostate size 30-80 mL 3
  • Open prostatectomy or enucleation techniques are recommended for prostate size >80 mL 3

Factors Affecting Prostate Volume

• Age is the primary determinant of prostate volume, with continuous growth throughout adulthood 2, 1
• Ethnicity may influence prostate volume, though most studies have predominantly included Caucasian populations 3
• Hormonal factors, particularly dihydrotestosterone (DHT), play a significant role in prostate growth 7
• Treatment with 5-ARIs like finasteride can reduce prostate volume by approximately 18% over 4 years 7

Understanding normal prostate volume ranges is essential for proper assessment of patients with lower urinary tract symptoms and for guiding appropriate treatment selection for benign prostatic hyperplasia.